A novel optical comb filter is designed with two cascaded phase-shifted linearly chirped fiber gratings.According to the transmission matrix method and Fabry-Perot resonant cavity theory,the characteristics of reflection spectrum of the optical comb filter are numerically analyzed for the different combinations of two chirp gratings,the value of chirp,the index modulation and the phase-shift.The results show that the distribute density of reflection peaks is different for the different combinations of two chirp gratings,that is,the spacing between reflection peaks is equal if the signs of two chirps same,it can be used to design a uniform filter; on the other hand,the distribute of reflection peaks shows the characteristic density gradient if the signs of two chirps opposite,which can be used to design a non-uniform filter.And the greater the chirp of gratings,the wider the bandwidth of reflection spectrum of the filter,and the lower the reflectivity; however, the reflectivity will be improved with the increase of index modulation; furthermore each of the reflection peaks moves with the change of phase-shift,which is useful to select a filter window by changing the phase-shift.